Sure! What you’re looking for is a .sublime-settings file. To create settings that will apply to all file types, create a “Base File.sublime-settings” file in your package directory (alongside your plugin’s .py file). The user will be able to override the defaults set in that file by adding the settings to the “User/Base File.sublime-settings” file.

Alternatively, if you don't want to use the file settings, you can use "MyPlugin.sublime-settings", and load the settings via sublime.load_settings("MyPlugin.sublime-settings") - see http://www.sublimetext.com/docs/2/api_reference.html. This will still use the standard merging facilities, so you can specify platform specific overrides in "MyPlugin (OSX).sublime-settings" and user specific overrides in "User/MyPlugin.sublime-settings"